Redox reactions is used to refer certain reactions in chemistry. Lets take a closer look at these reactions.
Look at the following reaction
Copper+ Oxygen -> Copper(II) oxide
2 Cu (s) + O2 (g) -> 2 CuO (s)
In this reaction copper has gained oxygen to become copper oxide. This reaction is an Oxidation reaction. Copper has Oxidized in this reaction.
Now lets look at another reaction
2HgO -> 2Hg + O2
Mercury oxide has removed oxygen to become mercury. This type of reaction is known as a reduction reaction. Mercury has reduced in this reaction.
Here is another reaction:
Lead (II) oxide + Hydrogen -> Lead + water
PbO (s) + H2 (g) -> Pb (s) + H2O (l)
Lead has reduced to lead in this reaction. Hydrogen has gained oxygen, oxidized in this reaction. Both oxidation and reduction has take place in the same reaction. Such reactions are referred as Redox reactions.
- Lead(II) Oxide has given oxygen to hydrogen to get oxidized . In simple words Lead(II) Oxide has helped another substance to oxidized. Therefore Lead(II) Oxide is an oxidizing agent.
- Hydrogen has taken oxygen from Lead(II) Oxide and 'helped' Lead(II) Oxide to reduce. Therefore Hydrogen is referred as a reducing agent.
However gaining or loosing of oxygen is not the only method of describing oxidation and reduction.
Na -e -> Na+
in this reaction sodium as given electrones to become sodium ion. This is also Oxydation.
2 Cl
According to this equation Chlorine has gained electrons. This is also reduction.
Loosing or gaining of Hydrogen can also be used to denote oxidation and reduction.
Loss of Hydrogen - Oxidation
Gain of Hydrogen- Reduction
and also if you are familiar with oxidation numbers
- When a substance undergo oxidation , its oxidation number increases
- Whan a substance reduces its oxidation number reduces.
Testing for oxidizing agents/ reducing agents:
There are substances which changes colour as they undergo oxidation/ reduction. They can be used to test whether a oxidizing agent or reducing agent is present in a solution.
Test for reducing agents:
1. adding Acidified potassium dicromate (VI) (K2Cr2O7)
It is a powerful oxidizing agent which can be used to identify a reducing agent. If a reducing agent is present in a solution, it will change the colour from orange to green
2. adding Acidified potassium permanganate (VII) (KMnO4)
If a reducing agent is present this will change colour from purple to colourless.
Test for oxidizing agents:
1. adding aqueous potassium iodide (KI)
If an oxidizing agent is present this will change colour from colourless to brown
Next about reversible reactions
3:36 AM
gained oxygen
Oxidation
Oxidized
oxidizing agent
Redox
Redox reactions
reduced
reducing agent
reduction
removed oxygen
Test for oxidizing agents
Test for reducing agents
